JPS6335931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a towing test for a model ship, and particularly to a method for determining the superiority or inferiority of hull resistance performance using a model ship. It is generally believed that in enlarged ships such as tankers, resistance is generated mainly in the front half of the hull due to the creation of waves or resistance due to wave collapse. Among these, the resistance component due to wave collapse can account for a considerable portion of the total resistance depending on the type of ship, and it is important to reduce wave collapse in order to improve the performance of this type of ship. . However, simply measuring the resistance value does not
It is impossible to separate this resistance component. Therefore, as an experimental method to compare the wave break resistance and find a better ship shape, conventionally, a model ship was created by changing the shape of a certain mother ship, and the resistance values of both were determined through experiments. It relies on an indirect method of comparison. Among the resistance acting on the hull, a method to separate and measure the resistance component caused by breaking waves is to use a pitot tube to carefully measure wakes around the hull or in the wake at multiple points. A method of detecting the generated water head loss, or recording the waves created by a ship using a wave height meter, and deducting the resistance corresponding to this measured waveform from the wave resistance component is considered to be the resistance component due to wave collapse. methods are being implemented. However, both of these methods
It requires a large amount of money and time to implement, such as the high cost of producing models and the need to repeat experiments many times to measure wakes and wave heights. In addition, as a document describing the conventional technology,
Volume 126 of the Journal of the Japan Society of Naval Architects, published in 1969, includes Eiichi Baba's “A New
Component of Viscous Resistance of Ships”
A paper entitled (A new component of viscous drag for ships) has been published. An object of the present invention is to provide a method for determining the superiority or inferiority of hull resistance performance, which makes it possible to determine the wave breaking resistance performance of a hull by a simple means without using wake measurement or wave height measurement of a model ship. . That is, based on the inventor's discovery that wave collapse near the water surface near the hull can be controlled by changing the shear flow on the free surface near the hull.
The purpose is to provide a method for determining the superiority or inferiority of hull resistance performance in terms of wave breaking resistance. Therefore, the method for determining the superiority or inferiority of hull resistance performance of the present invention involves measuring the towing resistance of a model ship while accelerating and decreasing the flow along the water surface near the hull of the model ship during a towing test of the model ship in a water tank. and determining the hull resistance curve of the model ship, determining the hull resistance curve of the model ship in the case where the flow along the water surface is not accelerated or decelerating, and detecting the mutual interval between these hull resistance curves. The method is characterized in that the wave breaking resistance performance of the model ship is determined by. In general, by slowing down the flow along the water surface, the wave collapse around the front half of the ship becomes more severe, and the hull resistance shows a high value, but it increases compared to the hull resistance value when the flow is not slowed down. is the amount of increase in hull resistance based on this additional wave breaking, and the more the shape of the front half of the hull is more likely to cause wave breaking (in other words, the worse the wave breaking resistance performance is), the more the flow along the surface increases. The degree of increase in resistance due to deceleration is large. Conversely, by accelerating the flow, the wave collapse around the front half of the hull is reduced and the hull resistance is reduced, but the reduced area is This is the amount of decrease in hull resistance commensurate with the reduction in wave collapse, and the more the front half of the hull is shaped to cause wave collapse (in other words, the wave collapse resistance performance is inferior), the greater the degree of resistance reduction due to the acceleration of the flow. Become. Therefore, the amount of increase in resistance when the flow along the water surface is decelerated or the increase in resistance when the flow is accelerated is compared to the hull resistance of a certain ship type without acceleration or deceleration of the flow as described above. If the amount of drag reduction is larger than that of other hull types, it can be easily separated and evaluated that the former hull type has inferior wave breaking performance, regardless of the overall resistance of both hull types. can. For the above-mentioned reasons, in the method for determining the superiority or inferiority of hull resistance performance of the present invention, the hull resistance curve of the model ship when the flow is accelerated and decelerated, and the hull resistance curve when the flow is accelerated and decelerated in a towing test of the model ship in a water tank. The distance between the hull resistance curve of the model ship and the hull resistance curve when there is no curve is detected, and it is determined that the narrower the distance, the better the wave breaking resistance performance of the model ship is. Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figures 1 and 2 are both side views showing a device used in the method for determining superiority or inferiority of hull resistance performance of the present invention, and Figure 3 is a layout of the device. A plan view showing an example, and FIGS. 4 and 5 are graphs showing hull resistance curves obtained by towing tests of model ships, respectively. In the apparatus shown in FIG. 1, a model boat 1 is suspended vertically in a water tank by a tow rod 4 via a resistance meter 3 from a tow wheel 2. A rotating belt 6 is installed so as to be in contact with the water surface 5 in front of the model ship 1. The rotating belt 6 is rotatably driven by a drive motor 8 on the towing wheel 2 via a chain or belt 7, and the rotating belt 6 is supported by a towing rod attached to the towing wheel 2. 9. By running the tow truck 2, the model ship 1
The boat travels with a rotating belt 6 in contact with the water surface 5 in front of it. At this time, the rotating belt 6 is rotated clockwise or counterclockwise at an appropriate speed, or stopped in some cases, depending on the test conditions. In this way, by rotating or stopping the rotating belt 6, the surface water on the water surface 5 is accelerated or decelerated compared to the case where the rotating belt 6 is not installed.
At this time, when the surface water is decelerated, the rotating belt 6
A more severe wave break occurs than in the normal case where there is no wave break, and conversely, when the surface water is accelerated, the wave break becomes less. When the surface water is decelerated or accelerated in this manner, wave breaking resistance increases or decreases compared to the test state in which the rotating belt 6 is not provided. At this time, if it is assumed that the interference between wave breaking resistance and other resistance components is small, the resistance value increased or decreased in this way can be compared with the increase or decrease in the resistance value of other ship types by the same means. Therefore, it is possible to compare the superiority and inferiority of ship shapes in terms of wave breaking resistance performance. Setting up this rotating belt 6 and conducting an experiment requires only one additional test cruise for the same speed at which a normal resistance test is measured, and dozens of times as in wake measurement using a pitot tube. does not require navigation. Further, since only the wave break resistance component can be increased or decreased independently using the simple method described above, it is possible to easily understand the relationship between the hull shape and the wave break resistance. As described above, according to the present invention, the test time for wave break resistance measurement can be significantly shortened. As a simple means to strengthen the shear flow along the water surface 5, as shown in FIG. You can just float your body 10. Further, as shown in FIG. 3, the rotating belt 6 and the membrane body 10 are located not only near the bow area A, but also near the front shoulder area B of the hull, near the rear shoulder area C of the hull, and near the stern area D.
It can be installed and tested near the ship's hull, where wave collapse is likely to occur. Next, an example of determining the superiority or inferiority of hull resistance performance using the method of the present invention based on the above test results will be explained. It is a hull resistance curve of hull type a against towing speed (ship speed),
The solid line graph in FIG. 5 is a hull resistance curve similarly obtained for hull type b. By comparing these hull resistance curves, it is difficult to determine the superiority or inferiority of the wave breaking resistance performance of the a and b hull types, but the method of the present invention determines the superiority or inferiority in the following manner. For example, with the rotation of the rotating belt 6 in Figure 1 stopped, that is, with the relative flow of surface water toward the bow being slowed down, the towing resistance of both model ships a and b was measured. Then, each hull resistance curve is determined as shown by the broken lines in Figures 4 and 5, respectively. As is clear from Figures 4 and 5, the reason why the resistance value increases from the solid line graph to the broken line graph is because the flow along the water surface 5 is decelerated by the device in Figure 1, resulting in wave breakage. This is due to an increase in resistance, and judging from the amount of increase in wave breaking resistance for both ship types a and b, the wave breaking resistance of ship type b is smaller than that of ship type a. In this way, it is determined that the hull type b, in which the gap between the hull resistance curves shown by the solid line and the broken line is smaller, has superior hull resistance performance. When the flow of surface water along the water surface 5 is accelerated toward the bow by the action of the rotating belt 6 in the device shown in FIG. 1, the hull resistance curve obtained by the towing test is It is shown that the resistance value shifts to the side where the resistance value is smaller than
The hull resistance performance of the model ship is judged to be excellent. As detailed above, according to the method of the present invention,
During a towing test of a model ship in an aquarium, the towing resistance of the model ship was measured while accelerating and decelerating the flow along the water surface near the hull of the model ship, and the hull resistance curve of the model ship was determined. The wave breaking resistance performance of the model ship is determined by determining the hull resistance curves of the model ship when the flow along the water surface is not accelerated or decelerating, and by detecting the mutual interval between these hull resistance curves. This method has the advantage of being able to very easily determine the superiority or inferiority of hull resistance performance from the perspective of wave breaking resistance, without having to conduct complicated comparative tests or wave height measurements using various hull shapes as in the past.

[Brief explanation of the drawing]

1 and 2 are both side views showing a device used in the method of determining superiority or inferiority of hull resistance performance of the present invention, FIG. 3 is a plan view showing an example of the arrangement of the device, and FIGS. Figure 5 is a graph showing hull resistance curves obtained by towing tests of model ships. 1...Model ship, 2...Tow truck, 3...Resistance meter,
4... Draw rod, 5... Water surface, 6... Rotating belt,
7... Chain or belt, 8... Drive motor, 9... Draw bar, 10... Membrane body, 11... Draw bar.

Claims (1)

[Claims] 1. During a towing test of a model ship in an aquarium, the towing resistance of the model ship is measured while accelerating and decelerating the flow along the water surface near the hull of the model ship, and the hull resistance curve of the model ship is determined. Determining wave breaking resistance performance of the model ship by determining the hull resistance curves of the model ship when the flow along the water surface is not accelerated or decelerating, and detecting the mutual interval between these hull resistance curves. A method for determining superiority or inferiority of hull resistance performance.